Anyone get worse gas mileage with SPDs y-pipe?

[imper]

Well i finally got the new y-pipe put one. And i was hope for a little better of something. Hell anything better. Instead everything is worse. I know how a lot more flutter noise than before. And i am now getting worse gas mileage. I run a lawn care biz and towing a 7,000lb trailer around town all day. Which i know is bad enough. But i normally got between 7.5mpg to 8.5mpg. Now after the new y-pipe im getting 6.1mpg. And it even went down to 4.8mpg one time. I have tried different octane fuel and changing driving style a little. But nothing helped. Has anyone had anything like this before? If this is the real problem then im going back to stock y-pipe. Oh and my truck is a 99 f250. Aftermarket headers and series 40 muffler.

[RagingBull2k2]

it almost sounds to me like its time for a good tuner... I'm looking to get this y-pipe installed into my truck in the next couple of weeks, but I've never heard of issues like this before...

Joey

[imper]

Originally Posted by RagingBull2k2

it almost sounds to me like its time for a good tuner... I'm looking to get this y-pipe installed into my truck in the next couple of weeks, but I've never heard of issues like this before...

Joey

By get a good tuner what do you mean?

[Stumpalump]

Can you reset the computer by un hooking the battery then turning on the light switch on Ford V10's? That makes some engines go through a learn cycle to compensate for changes.

[imper]

so i just need to reset the computer?

[dkf]

The y-pipe should not affect fuel mileage at all, if anything make it better. I'd make shure no O2 wires are still in good shape and were not damaged. Clean the MAF, replace the fuel filter if its due along with the air filter and reset the computer. The truck should relearn regardless but reset the computer anyway. Disconnect the battery lead and turn the headlight switch on for a little to bleed any excess voltage. Reconnect the to the battery and your trucks reset.

[Krewat]

It's a '99, so it didn't have the restricted y-pipe in the first place, so that's something to consider.

[imper]

Originally Posted by Krewat

It's a '99, so it didn't have the restricted y-pipe in the first place, so that's something to consider.

Yea i knew that. But i was hoping for anything better. Figured i was doing the headers might as well do the y-pipe.

Not to mention now the dang thing sounds like an old farm tractor.

[dkf]

Did you do the headers and the Y-pipe at the same time?

[saggys]

I did not notice a change in mileage but definetly seat of the pants change, especially on hills with my 99. I am towing 3800lb boat with a 3800lb slide in camper and am getting 8.75mpg combined mainly hiway.

[Krewat]

Any chance you have an exhaust leak before the O2 Sensors? That would introduce more oxygen into the exhaust, trick the O2 sensors into seeing a lean condition, and the PCM would fatten up the mixture ruining your gas mileage. ?

[saskdiesel]

Originally Posted by Krewat

Any chance you have an exhaust leak before the O2 Sensors? That would introduce more oxygen into the exhaust, trick the O2 sensors into seeing a lean condition, and the PCM would fatten up the mixture ruining your gas mileage. ?

Hmm.
I had massive exhaust leaks on both sides before I did the manifold bolts and gaskets. I thought this may make a bit of a difference.
Nope. Same milage and I just got back form a trip towing the travel trailer.

[johniebomb]

I had some of the same problem when I installed the SPD y pipe. My 2000 X went from sounding like a high reving race engine to a 6 cylinder farm truck. I did not see any noticable gas mileage increase the power seems to be slightly improved but it takes it longer to get there than before. If I had it to do over again I would have left it alone. Two questions, I just assumed that my factory rams horn had the restritors in it, could it not had, I did not get to look at it before the muffler guy tossed it. If it did not have the restrictors where could I get another one to replace the SPD? Thanks for the help.

[dkf]

Originally Posted by johniebomb

I had some of the same problem when I installed the SPD y pipe. My 2000 X went from sounding like a high reving race engine to a 6 cylinder farm truck. I did not see any noticable gas mileage increase the power seems to be slightly improved but it takes it longer to get there than before. If I had it to do over again I would have left it alone. Two questions, I just assumed that my factory rams horn had the restritors in it, could it not had, I did not get to look at it before the muffler guy tossed it. If it did not have the restrictors where could I get another one to replace the SPD? Thanks for the help.

The sticky above basically proves the "Rams Horn" Y doesn't hurt performance. The stock tuning is horrible and if you want better performance get an SCT tuner from 5 star. The SPD can change the sound some, especially when you have a non OE exhaust on it.

[Krewat]

I have to keep remembering that I had the eBay headers in first, and THEN went to the eBay Y-pipe. It definitely woke up the low-end, that's for sure. But again, cart leading the horse kinda thing.